NJECTION-MOULDING seminar report prasention.ppt

Injection

1. PLASTIC INJECTION MOLDING
AKASH DEEP.B.N
1SJ03ME121

2. Plastic Injection Molding
 Overview
 Injection Molding
 Injection Molding machine
 Injection molding processes
Injection molding materials
Injection molding problems and solutions
 Typical applications and Products

3. Overview
Injection molding is the most widely used polymeric fabrication
process.
It is the primary process for manufacturing thermo plastic
products.
Injection molding can be used to form a wide variety of products.
Complexity is virtually unlimited, sizes may range from very
small to very large, and excellent control of tolerances is also
possible.
The major reasons that injection is so popular is that it produces
light weight parts of specific color with built in surface texturing.
Most polymers may be injection molded, including
thermoplastics, fiber reinforces thermoplastics, thermosetting
plastics, and elastomers.

4. Injection molding
Injection molding is a method to obtain molded products by injecting
plastic materials molten by heat into a mold, and then cooling and
solidifying them.
The method is suitable for the mass production of products with
complicated shapes, and takes a large part in the area of plastic processing.
Advantages of Injection Molding
High production rates
Wide range of materials can be used
Low labor costs
Minimal scrap losses

5. Types of Injection Molding Machines
Hand injection molding machine
Piston type injection molding machine
Reciprocating type injection molding
machine

6. Injection Molding Machine

7. Injection molding machine is divided into 3 units i.e.
a clamping unit, an injection unit and mold.
The functions of the clamping unit are opening and
closing a die, and the ejection of products. There are
2 types of clamping methods, namely the toggle type
shown in the figure below and the straight-hydraulic
type in which a mold is directly opened and closed
with a hydraulic cylinder.
The functions of the injection unit are to melt plastic
by heat and then to inject molten plastic into a mold.

9. Machine components
Injection system
The injection system consists of a hopper, a reciprocating screw and
barrel assembly, and an injection nozzle, as shown in Figure 1. This
system confines and transports the plastic as it progresses through the
feeding, compressing, degassing, melting, injection, and packing stages.
 FIGURE 1. A single screw injection molding machine for
thermoplastics, showing the plasticizing screw, a barrel, band heaters to
heat the barrel, a stationary platen, and a movable platen.

10. The hopper
The barrel
The reciprocating screw
The reciprocating screw is used to compress,
melt, and convey the material. The reciprocating
screw consists of three zones (illustrated below)
the feeding zone
the compressing (or transition) zone
the metering zone

11. FIGURE 2. A reciprocating screw, showing the feeding
zone, compressing (or transition) zone, and metering
zone.

12. The nozzle
FIGURE 3. (a) Nozzle with barrel in processing position. (b) Nozzle with
barrel backed out for purging.
Mold system
The mold system consists of tie bars, stationary and moving platens, as
well as molding plates (bases) that house the cavity, sprue and runner
systems, ejector pins, and cooling channels, as shown in Figure 4. The
mold is essentially a heat exchanger in which the molten thermoplastic
solidifies to the desired shape and dimensional details defined by the
cavity.

13. Mold System
3 plate mold 2 plate mold

14. Hydraulic system
Control system
Clamping system
The delivery system
The delivery system, which
provides passage for the molten
plastic from the machine nozzle to
the part cavity, generally includes:
a sprue
cold slug wells
a main runner
branch runners
gates.
FIGURE 6. The molded system
includes a delivery system and molded parts.

15. Injection molding processes
The Injection molding process
basically is divided into 6 major
steps
1. Clamping
2. Injection
3. Dwelling
4. Cooling
5. Mold Opening
6. Ejection

16. Cycle time in injection molding
The injection molding cycle can be divided
into several stages. They aremold closing,
filling, packing, cooling, mold opening and
ejection as shown here.
Cooling Time is a major fraction of the total
cycle time.
Materials for injection molding
Acrylonitrile butadiene styrene (ABS)
Polyethylene
Polypropelene
Polystyrene

17. Typical Applications
Injection molding is widely used in a wide variety of
industries: automotive, appliance, computer,
communication and industrial equipment. Examples of
injection molded parts in the automotive industry include
sail panels, radiator end caps, door panels, lamp housings,
and fuel rails.
    
Automobile parts Automotive Sail Panel Radiator End Cap  Fuel Rails with Injectors

18. Injection Molding Problems and
Solutions
Fault
Air trap
Black streaks
Flash
Short shot
Sink mark
Solution
Reduce injection speed,
Proper venting.
Lower the barrel temp.
Clean the injection unit.
Adjust the clamp force.
Reduce the injection pressure.
Increase the injection value.
Increase the cooling time.

19. Conclusion
As the injection molding technology is now
living its most rapid development times. The
most important factors behind this situation is
There is no potential competitors
Injection molding is especially suitable for mass
production.
The profitable molding in today’s competitive
market depends on precise clamping action
coupled with both high plasticizing performance
and reliability integrated with complete plant
operating performance.

20. References
Injection Molding Hand Book
Dominick V Rosato
Donald V Rosato
Theory of Molds
R S Nagesh
WWW.Google.com